Recently, semiconductor integrated circuit devices have been miniaturized. As the miniaturization proceeds, various thin films used in the semiconductor integrated circuit devices are required to be further thinned and to have better film quality.
For example, a related art discloses a method of forming an insulating film, such as a oxide film.
For further thinning of a film, it is important to improve a surface roughness of the thin film. This is because it is difficult to obtain a thin film having a uniform film thickness when there is poor surface roughness.
In addition, as a new problem in the thin film, it has also been important to improve interface roughness with a base. If the interface roughness is poor, interface states occur in an interface between the base and the thin film, and thus, mobility of electrons or holes may deteriorate or electrical charges may be trapped.
A related art discloses formation of a thin oxide film or an improvement of electrical characteristics of the thin oxide film, but does not disclose improvements of surface roughness and interface roughness.